The Midwest has experienced some stretches of below-normal temperatures, with cold, rainy conditions this spring. Research shows that the opportune time to plant corn is somewhere between the last two weeks of April and the first few days of May. However, Mother Nature isn’t necessarily on that same schedule. Fields that have been recently planted or those that will be planted in the next couple days may be subject to seedling injury.

SIGNS OF INJURY

Corn that has been recently planted in the Midwest has experienced less-than-ideal overall conditions, especially when it comes to temperature. In many locations, the weather pattern of cold rain and low temperatures has potential to promote a problem for young seedlings called “Imbibitional Chilling Injury.” Some basic visual symptoms may be corkscrewing of the young germinating plant or leafing out below ground level. Consider digging up a few seedlings and checking them for signs of corkscrewing, leafing out underground or damping off.

WHY WOULD SEEDLINGS REACT LIKE THIS?

A possible issue that cause less than optimum stands and poor emergence is chilling injury to the mesocotyl or coleoptile plant tissue caused by sub-lethal cold temperatures (less than 50 degrees) during the period very soon after planting when seeds begin to imbibe water. The seed will not begin to germinate until the soil temp approaches 50 degrees, however, the seed will allow water to enter regardless of temperature. This chilling injury basically equates to cells rupturing which results in the corkscrewing of the mesocotyl. This delays the emergence of the coleoptile prior to the usual emergence of leaves from the coleoptile.

In addition to slowing the germination process, cold temperatures, snow and cold rains may cause irreparable harm to the delicate structures of an emerging corn seedling. When dry corn seed absorbs cold water, Imbibitional Chilling Injury is not uncommon. Such injury in corn seeds ruptures cell membranes and results in aborted radicles, proliferation of seminal roots, delayed seedling growth and potential for diseases pathogens to attack the young seedling. When temperatures remain at or below 50 degrees Fahrenheit after planting or fall below 50 degrees within 24-48 after planting, damage to germinating seed can be particularly severe as they imbibe water. This should be considered as there is risk associated with the temperature and moisture roller coaster we have experienced so far this planting season.

If you have any questions, contact your local Hoegemeyer agronomist or District Sales Manager.

A significant frost and freeze event occurred this past week across a wide area in the Western Corn Belt. Temps dropped to the mid to upper 20’s the morning of May 16th. Luckily it appears most of the corn to the north where temps were the coldest was only in the spike to 1 leaf stage which enabled it to readily survive. Areas further to the south have shown more damage to above ground tissue since a lot of the corn was at the 2-4 leaf stage. However, overnight temps do not appear to have dropped below 28 degrees for long enough to cause significant plant death. The growing point does not rise above the soil surface until about V6. At this time the vast majority of fields appear to have begun to recover with new healthy re-growth in the last 2-3 days aided by the recent sunny warm days. This current warm spell is just what these plants need in order to rapidly recover. By this time it should be fairly easy to determine the level of actual plant death in these fields. From what I have seen, there appears to be very little to no actual death in most fields. Growers who have been out in their fields feel much better than they did a few days ago. However, many are concerned about the large number of plants in fields that are exhibiting leaf whorl tie-up where the dead leaf tissue meets the new tissue that has recently re-grown. The vast majority of these tied-up plants should break free and unravel within the next few days. Warm and windy days are once again just what the doctor ordered. As the dead tissue continues to decay it will likely separate from the new re-growth and allow the whorl to unravel. Bob Nielsen with Purdue University Agronomy states, “The dead tissue of the damaged part of the whorl may restrict this leaf extension for awhile, but in most cases will not restrict it completely.”

It is possible that some plants in these fields will not unravel properly resulting in a lost plant but if past events tell us anything, it should be minimal. Just as was the case 1-2 days after the freeze/frost itself, there really is nothing to do but wait. Go back and check these fields in another 3-4 days. There will likely be significant improvement. Making a decision to replant at this time would not be wise. If you have more questions regarding frost/freeze damage contact your local Hoegemeyer DSM or Agronomist.

It’s barely the 1st of April and the weather as of the last several weeks has things looking more like early May at the very least. Soil temps are well above normal for this time of year and seed bed conditions are looking good. Corn planted now will rapidly begin the germination process as long as adequate moisture is present. That’s a good thing. However, let’s list a few risks associated with the possibility of extremely early planting dates this year………. The average last freeze in Omaha, NE is around April 20th based off of historical data. As you move north and west that date creeps later on the average. As mentioned earlier, corn planted now has the potential to germinate, emerge, and begin leaf develop quickly if this weather pattern holds. There would be the possibility of a significant killing freeze to corn with the growing point near the soil surface if a late April freeze would occur. Worth noting is also the situation with seed supply this year after a more than challenging production year last summer. If replant seed is needed on many acres it will be very difficult to supply the same hybrid that was originally planted. Very tight seed supplies on popular products would force another choice not to mention replacement seed policies for replant will not be honored unless dates are past the insurance coverage dates for the geography in question. We have always been in favor of early planting dates for increased yield potential. However, this year is shaping up to be almost a little crazy in terms of “early”. A few fields along the Interstate 80 corridor went in the ground this past week before the calendar even made it out of March! As always, spreading risk makes the most sense in many aspects of production agriculture. With today’s planting equipment, many growers have the ability to plant an incredible amount of acres in only a few days. Hopefully, this blog post will be nothing more than crying wolf and we end up with early planting dates, good emergence, and no freeze. However, we will have to be willing to accept the possible risk if all of our corn goes in the ground in a condensed time frame way ahead of normal. Maybe this year we will have the chance to slow down and spread things out a little??

As some of you may have encountered a frost last night, here is some information from 'The Chat 'n Chew Cafe' from Purdue University that I found which I hope will be helpful if you might be looking at any frosted fields.

- Lethal cold temperatures are more damaging than “simple” frost.

- Leaf injury or death does not guarantee plant death or yield loss.

- Patience is a virtue when waiting for crops to indicate their recovery.

When contemplating the effects of frost injury to corn and soybean, it is important to recognize that the extent of crop injury depends quite a bit on whether the field experienced lethal cold temperatures or “simple” frost. Lethal cold temperatures for corn and soybean are those at or below 28 degree F. A definition of “simple” frost is that which occurs at temperatures warmer than 28 degree F.

At young developmental stages, soybean is more susceptible than corn to above-ground damage by frost or lethal cold temperatures because its growing points are exposed above ground as soon as the crop emerges. Soybean axillary buds develop at each leaf axil of a soybean plant, including the cotyledons. Recovery from frost damage is possible if any of these buds remain alive. Frost or freeze damage extending below the cotyledons translates to complete death of the seedling.

The growing point region of a corn plant remains below ground until about the 5-leaf collar stage and, thus, is reasonably protected from the effects of above-ground frost. Consequently, the effects of “simple” frost damage to corn are usually minor and limited to death of above-ground plant parts. Corn can easily recover from this type of damage early in its development and suffer no yield loss whatsoever.

When air temperatures actually drop to lethal levels (28 degree F or less) for more than a few hours, the growing point region of a young corn plant can be injured or killed even if it is still below the soil surface. Consequently, one of the key factors that determine whether corn will recover from frost damage is whether lethal cold temperatures accompany the frost. This distinction between damage by frost and lethal temperatures is the reason why experience with frost damage may differ from a neighbor’s experiences.

The key requirement for assessing frost damage to either corn or soybean is to be patient and allow the plants to show you whether they are capable of recovering. While corn and soybean leaves may blacken and wither within a day after frost occurs, the true extent of plant damage may not yet be discernible.

The bottom line on diagnosing the severity of frost or low temperature injury to corn or soybean is that you generally need to wait three to five days after the weather event before you can accurately assess the extent of damage or recovery. Recognize that cool days following a frost event may slow the plants’ recovery and delay your ability to assess their health.

These three to five days will be better spent continuing to plant the remainder of your crop acres, assuming that most growers are not yet finished with corn and soybean planting. After that period of time, recovery of the surviving plants should be evident while those plants that are truly dead will not exhibit signs of recovery.

After three to five days, surviving corn plants should be showing new leaf tissue expanding from the whorls, while dead corn plants will still look dead. Surviving soybean plants will show new leaves emerging from one or more of the uppermost undamaged nodes, while dead plants will still look dead.

Yield loss to early season frost damage in corn and soybean is related primarily to the degree of stand loss, not to the degree of leaf damage. The dead tissue of the damaged part of the whorl may restrict this leaf extension for a while, but in most cases will not restrict it completely. Mowing of frost-damaged corn to encourage its recovery is rarely justified.

If recovery is evident after three to five days, then replanting is not justified. If a significant proportion of the population is obviously dead after this same period of time, then replanting may be justified.